1. Field of the Invention
This invention relates to a rotation phase control device and more particularly to a device for controlling a rotation phase by carrying out at least an integrating process on phase error information.
2. Description of the Related Art
In arranging a rotation phase control device to control the rotation phase of a rotary body for rotating it in synchronism with a given reference phase, it has generally been practiced to arrange, in combination with the rotation phase control device, a rotation speed control device for controlling a rotation speed on the basis of rotation speed information obtained from the rotary body. More specifically, while the rotary body is allowed to rotate at a speed close to a desired rotation speed under the control of the rotation speed control device, a phase difference between the rotation phase information obtained from the rotary body and the reference phase information is detected. Then, the rotation phase is controlled according to a phase error signal which is formed on the basis of information on the phase difference detected.
For stronger and stabler phase control, the rotation phase control device is generally provided with a phase compensating circuit which acts mainly as an integrating circuit. The above-stated phase error signal is supplied as a phase control signal via this phase compensating circuit to a rotary body driving system.
However, the integrating time constant of the phase compensating circuit is sometimes set at a relatively large value. In that case, the stability of the device in a normal operating state increases. However, with regard to the response characteristic of the device in a transient state, its control locking-in time becomes long.
In cases where the mixing ratio of the phase control signal to the speed control signal is increased for stronger phase control, the rotation phase approaches to the desired phase often after over-shooting. In some extreme cases, it brings about hunting, thus resulting in an excessively long locking-in time.